The present invention relates to a plasma processing apparatus or a plasma processing method for processing a substrate sample such as a semiconductor wafer disposed in a processing chamber inside a vacuum container using a plasma generated in the processing chamber, and more particularly to a plasma processing apparatus or a plasma processing method for processing the sample while determining the thickness or depth of a film during processing using light from a sample surface.
For semiconductor wafer fabrication, dry etching is widely used to remove a layer made of various materials formed on a wafer surface and particularly to remove a layer made of a dielectric material or to form a pattern thereon. The dry etching device plasmarizes a process gas introduced in the processing chamber inside the vacuum container to form ions and radicals, which are made to react with a wafer for wafer etching processing.
In a dry etching process of a semiconductor wafer, emitted-light intensity of a specific wavelength in plasma light changes with progress of etching of a member to be processed. In view of this, there is a conventional method of detecting a semiconductor wafer etching end point, in which a change in emitted-light intensity of a specific wavelength is detected from a plasma during the dry etching process and based on the detection results, the etching end point where the member to be processed is completely removed by etching is detected.
For example, there is a process of applying a mask material on the wafer and then etching a silicon substrate to form a groove for electrically isolating elements on the wafer in the silicon substrate. In this case, it is important to etch the silicon substrate to a predetermined depth amount before terminating the process.
Examples of the method include a method in which when plasma light is observed using optical emission spectroscopy, silicon depth increases with etching progress; light dispersed thereby forms an interference waveform, and an interference signal corresponding to the interference waveform is used to measure the depth.
There is known a method disclosed in JP-A-2010-34582, where a known light beam from outside is incident on a wafer, the wavelength of three light beams reflected from the wafer are observed, and a frequency analysis is performed thereon to calculate the etching depth.
There is known another method disclosed in JP-A-2003-83720, where interference light produced by plasma light reflected by the member to be processed is observed and the interference waveform is separated into a mask component and a step component by a wavelength band to calculate the etching depth.